To qualify as an heirloom, a seed cannot be a hybrid. All heirlooms are old-fashioned varieties, generally at least 50 years old. Many heirloom seeds have been passed down through families, although commercial companies sometimes specialize in selling heirlooms. Organic seeds, on the other hand, can be either heirloom or hybrid.
In order to be certified organic, there must have been no chemicals used in the growing of these plants and seeds. Natural fertilizers and pesticides such as compost, bone meal and soap sprays are allowed. The U.S. Department of Agriculture will test plants and soil thoroughly before certifying any seeds organic. Heirloom seeds, while often grown organically, do not necessarily have to be that way.
Organic seeds and heirloom seeds may be planted in the same garden, but only if certain conditions have been met. In order to remain organic, you must only use natural methods for fertilization and pest control. No chemicals are allowed for organic produce. You must plant heirloom seeds separately from other heirloom seeds of the same type to reduce any chance of cross-pollination. Many heirloom seed growers love to save seeds year after year. Keep similar varieties away to keep your seed's parentage clear.